The present application is a 371 of PCT/NZ97/00134, filed Oct. 9, 1997, and claims priority from New Zealand patent application Serial No. 299537, filed Oct. 9, 1996.
This invention relates generally to immunological reagents (antibodies) capable of binding to activated dendritic cells, to cell lines which express such antibodies and to a process for identifying and purifying dendritic cells from blood using such antibodies.
Dendritic cells (DC) constitute a distinct group of potent antigen presenting cells (APC) which are bone marrow derived and found as trace populations in the circulation as well as within both lymphoid and nonlymphoid tissues1-3. Although their importance as the most effective haemopoletic cell involved in the initiation of primary immune responses has been well demonstrated4-7, no human DC specific lineage marker has been identified and most features of their ontogeny and relationship to other leukocytes remains unclear.
Phenotypically, human DC are characterised1-3.7-11 by a high density of class II MHC antigens, the presence of a wide range of adhesion molecules and the absence or low expression of a range of lineage specific cell surface antigens (CD3, CD14, CD16, CD 19, CD57). A number of activation antigens including IRAC12, HB1513, 4F28, IL-2R7.8, and B7/BB-17.14 have also been reported on human DC, particularly after activation, although the anti-IRAC and HB15 reagents have not been shown to stain isolated fresh blood DC. Despite this phenotypic characterisation, identification and therefore purification of DC remains difficult as the majority of these antigens are expressed by other resting and activated cell types. Many of the functional and phenotypic features of DC are shared by both Hodgkins cells (HC) and Hodgkins Disease (HD) derived cell lines and there is increasing evidence to support the hypothesis, that in some instances, HC represent a malignant form of DC15-17.
Immunological reagents for use in a process for identifying and purifying DC therefore have obvious utility. Such reagents will need to recognize epitopes or antigens specific to DC. To date antibodies have been generated against early activation antigens CD8318.19 and CMRF-4420. However, there remains a need to have available antibodies which can bind to different epitopes on DC than CD83 and CMRF-44.
It is therefore an object of this invention to provide immunological reagents which recognise epitope(s) of a novel activation antigen found on DC or at least provide the public with a useful choice.
In a first aspect the present invention can be said to provide antibodies or binding fragments thereof which specifically bind to DC activation antigen CMRF-56.
Conveniently, the antibody is a monoclonal antibody, preferably monoclonal antibody CMRF-56 (mAb CMRF-56).
In yet a further aspect, the invention provides hybridoma cell line CMRF-56.
In still a further aspect, the present invention provides mAb CMRF-56 secreted by hybridoma cell line CMRF-56 which specifically binds to an epitope on activated human DC but does not bind to activation antigens CMRF-44 and CD83.
In yet a further aspect, the invention provides an antibody or antibody binding fragment which is specific for the epitope on human DC to which mAb CMRF-56 binds.
In still a further aspect, the present invention provides a process for identifying activated DC in a sample containing such cells comprising the step of contacting said sample with an antibody or antibody binding fragment as defined above.
In yet a further aspect, the invention provides a process for purifying and/or concentrating DC from a sample containing such cells comprising the step of contacting said sample with an antibody or antibody binding fragment as defined above.
In the preferred embodiment of these processes, the cells to be identified or purified are activated human DC and the antibody is mAb CMRF-56.
In still a further aspect, the invention provides a DC purification system for use in purifying or concentrating DC from a sample containing such cells which includes an antibody or antibody binding fragment as defined above.
Conveniently, the purification system is designed to purify activated human DC and the antibody is optionally labelled mAb CMRF-56.
In still a further aspect, the present invention consists in activated DC recovered by a process as defined above or by using a purification system as defined above.
In yet a further aspect, the invention provides an immunopotentiating composition comprising activated DC obtained as above and at least one antigen capable of generating a protective immunological response to a disease in an animal susceptible to such disease.
In still a further aspect, the invention provides an immunopotentiating composition comprising an antibody as defined above and at least one antigen capable of generating a protective immunological response to a disease in a patient susceptible to such disease.
In still a further aspect, the invention provides an immunopotentiating composition comprising activated DC obtained as above, an antibody as defined above and at least one antigen capable of generating a protective immunological response to a disease in a patient susceptible to such disease.
In still a further aspect, the invention provides an immunopotentiating composition comprising an antibody as defined above.
In still a further embodiment, the invention provides a method of prophylaxis and/or therapy in relation to a disease which comprises administering to a subject susceptible to said disease an immunopotentiating composition as defined above.
In yet a further aspect, the invention provides an assay kit which includes mAb CMRF-56 for use as a diagnostic marker of activated DC.